Problem: Windows 2000 Messenger Spam
pop-up ads constantly appearing on Microsoft Windows computers

Solution:
Disable the messenger service running on background.
    1) go to "Start Menu" => "Settings" => "Control Panel" => "Administrative Tool" => "Services"
    2) find "Messenger", right click and choose "Properties"
    3) under "Startup type," choose "Disabled"

If you would like more information on this problem, click here.